X-Message-Number: 7670
Date: Sat, 08 Feb 1997 21:25:42 -0400 (EDT)
Subject: Cryo Journal Club 1

Date sent:  8-FEB-1997 21:10:25 
The following abstract was published in Cryobiology. The author concluded that
vitrification,  melting, or temperature fluctuation  per se did not affect
embryonic survival.
One might conclude from this experiment that it would be safe to replace one
cryo protectant with another in cryo patients as long as cooling and warming 
is done under moderate conditions.


Fracture Damage of Embryos and Its Prevention during Vitrification and Warming

M. Kasai, S. E. Zhu, P. B. Pedro, K. Nakamura, T. Sakurai, K. Edashige

The frequency of fracture damage in mouse blastocysts was examined by repeated
cycles of vitrification and warming. Mouse blastocysts suspended in a solution
of ethylene glycol, Ficoll, and sucrose in a straw were plunged into liquid
nitrogen either directly (rapidly) or after holding them in liquid nitrogen
vapor for 3 min or more (moderately). Vitrified samples were warmed by
plunging them into 25C water either immediately (rapidly) or after holding
in air for 5-30 s (moderately). Warmed straws were recooled and rewarmed up to 
9 times,
to exaggerate the effect of cooling and warming. When embryos were cooled and
warmed rapidly once, the incidence of the zona damage was only 1.2%, and 91%

of recovered embryos reexpanded in culture. However, with repeated rapid cooling
and warming, the incidence of zona damage increased, reaching 75% after 10
vitrifications; survival also dropped. When embryos were subjected to 10
cycles of moderate cooling and moderate warming with 15 or 30 s of suspension 
in air,  100% of the embryos had intact zonae. On the other hand, with 
moderate cooling followed by rapid warming or with rapid cooling followed by 
moderate warming,
41 and 16% of embryos had damaged zona, respectively, after 10 vitrifications.
Therefore, fracture damage occurs during both cooling and warming, but it can
be prevented completely by employing somewhat slower rates of cooling and
warming. Furthermore, a high survival rate (88%) after 10 cycles of moderate
cooling and moderate warming with 15 s of suspension in air indicates that
vitrification, melting, or temperature fluctuation per se do not affect
embryonic survival.


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